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perf: reduce header validation and pseudo-header extraction passes #268

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218 changes: 142 additions & 76 deletions lib/headers.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -160,13 +160,21 @@ let get_multi t name =
let get_multi_pseudo t name = get_multi t (":" ^ name)

module Pseudo = struct
let reserved_request = [ ":method"; ":scheme"; ":authority"; ":path" ]
let reserved_response = [ ":status" ]

(* 0x3A is the char code for `:` *)
let is_pseudo name = Char.code (String.unsafe_get name 0) = 0x3A
end

let is_reserved_pseudo_header ~is_request name =
if is_request
then
match name with
| ":method" | ":scheme" | ":authority" | ":path" -> true
| _ -> false
else
match name with
| ":status" -> true
| _ -> false

(* Headers are stored in reverse transmission order. Iterate in wire/HPACK order
* without allocating an intermediate reversed list. *)
let iter_hpack ~f t =
Expand All @@ -186,80 +194,138 @@ let fold ~f ~init t =

let exists ~f t = List.exists (fun { name; value; _ } -> f name value) t

type request_headers_scan =
{ valid : bool
; method_count : int
; method_value : string option
; scheme_count : int
; scheme_value : string option
; path_count : int
; path_value : string option
; has_authority : bool
}

let validate_headers ~is_request t =
let pseudo_ended = ref false in
let has_connection = ref false in
let invalid_te = ref false in
let exception Invalid_headers in
try
iter_hpack
~f:(fun { name; value; _ } ->
let is_pseudo = Pseudo.is_pseudo name in
let pseudo_did_end = !pseudo_ended in
if (not is_pseudo) && not pseudo_did_end then pseudo_ended := true;
if
(* From RFC7540§8.1.2:
* [...] header field names MUST be converted to lowercase
* prior to their encoding in HTTP/2. A request or response
* containing uppercase header field names MUST be treated as
* malformed (Section 8.1.2.6). *)
(not (CI.is_lowercase name))
(* From RFC7540§8.1.2.1:
* Pseudo-header fields are only valid in the context in
* which they are defined. [...] pseudo-header fields defined
* for responses MUST NOT appear in requests. [...] Endpoints
* MUST treat a request or response that contains undefined
* or invalid pseudo-header fields as malformed (Section
* 8.1.2.6). *)
|| (is_pseudo && not (is_reserved_pseudo_header ~is_request name))
||
(* From RFC7540§8.1.2.1:
* All pseudo-header fields MUST appear in the header block before
* regular header fields. Any request or response that contains a
* pseudo-header field that appears in a header block after a
* regular header field MUST be treated as malformed (Section
* 8.1.2.6). *)
(is_pseudo && pseudo_did_end)
then raise Invalid_headers;
if CI.equal name "connection"
then has_connection := true
else if CI.equal name "te" && value <> "trailers"
then invalid_te := true)
t;
not !has_connection && not !invalid_te
with
| Invalid_headers -> false

let scan_request_headers t =
let pseudo_ended = ref false in
let has_connection = ref false in
let invalid_te = ref false in
let method_count = ref 0 in
let method_value = ref None in
let scheme_count = ref 0 in
let scheme_value = ref None in
let path_count = ref 0 in
let path_value = ref None in
let has_authority = ref false in
let exception Invalid_headers in
let valid =
try
iter_hpack
~f:(fun { name; value; _ } ->
let is_pseudo = Pseudo.is_pseudo name in
let pseudo_did_end = !pseudo_ended in
if (not is_pseudo) && not pseudo_did_end then pseudo_ended := true;
if
(not (CI.is_lowercase name))
|| (is_pseudo && not (is_reserved_pseudo_header ~is_request:true name))
|| (is_pseudo && pseudo_did_end)
then raise Invalid_headers;
if CI.equal name "connection"
then has_connection := true
else if CI.equal name "te" && value <> "trailers"
then invalid_te := true
else if CI.equal name ":method"
then (
incr method_count;
if !method_value = None then method_value := Some value)
else if CI.equal name ":scheme"
then (
incr scheme_count;
if !scheme_value = None then scheme_value := Some value)
else if CI.equal name ":path"
then (
incr path_count;
if !path_value = None then path_value := Some value)
else if CI.equal name ":authority"
then has_authority := true)
t;
not !has_connection && not !invalid_te
with
| Invalid_headers -> false
in
{ valid
; method_count = !method_count
; method_value = !method_value
; scheme_count = !scheme_count
; scheme_value = !scheme_value
; path_count = !path_count
; path_value = !path_value
; has_authority = !has_authority
}

let valid_headers ?(is_request = true) t =
match get t "connection", get t "TE" with
| Some _, _ ->
(* From RFC7540§8.1.2.2:
* HTTP/2 does not use the Connection header field to indicate
* connection-specific header fields; in this protocol,
* connection-specific metadata is conveyed by other means. An endpoint
* MUST NOT generate an HTTP/2 message containing connection-specific
* header fields; any message containing connection-specific header
* fields MUST be treated as malformed (Section 8.1.2.6). *)
false
| _, Some value when value <> "trailers" ->
(* From RFC7540§8.1.2.2:
* The only exception to this is the TE header field, which MAY be
* present in an HTTP/2 request; when it is, it MUST NOT contain any
* value other than "trailers". *)
false
| _ ->
let pseudo_ended = ref false in
let exception Invalid_headers in
let invalid =
try
iter_hpack
~f:(fun { name; _ } ->
let is_pseudo = Pseudo.is_pseudo name in
let pseudo_did_end = !pseudo_ended in
if (not is_pseudo) && not pseudo_did_end then pseudo_ended := true;
if
(* From RFC7540§8.1.2:
* [...] header field names MUST be converted to lowercase
* prior to their encoding in HTTP/2. A request or response
* containing uppercase header field names MUST be treated as
* malformed (Section 8.1.2.6). *)
(not CI.(is_lowercase name))
(* From RFC7540§8.1.2.1:
* Pseudo-header fields are only valid in the context in
* which they are defined. [...] pseudo-header fields defined
* for responses MUST NOT appear in requests. [...] Endpoints
* MUST treat a request or response that contains undefined
* or invalid pseudo-header fields as malformed (Section
* 8.1.2.6). *)
|| (is_pseudo
&& not
(List.mem
name
(if is_request
then Pseudo.reserved_request
else Pseudo.reserved_response)))
||
(* From RFC7540§8.1.2.1:
* All pseudo-header fields MUST appear in the header block before
* regular header fields. Any request or response that contains a
* pseudo-header field that appears in a header block after a
* regular header field MUST be treated as malformed (Section
* 8.1.2.6). *)
(is_pseudo && pseudo_did_end)
then raise Invalid_headers)
t;
false
with
| Invalid_headers -> true
in
not invalid
if is_request then (scan_request_headers t).valid else validate_headers ~is_request t

let valid_request_headers t = valid_headers t
let valid_response_headers t = valid_headers ~is_request:false t

let method_path_and_scheme_or_malformed t =
match
( get_multi_pseudo t "method"
, get_multi_pseudo t "scheme"
, get_multi_pseudo t "path" )
with
| _, [ ("http" | "https") ], [ path ] when String.length path = 0 ->
let { valid
; method_count
; method_value
; scheme_count
; scheme_value
; path_count
; path_value
; has_authority
} =
scan_request_headers t
in
match method_count, method_value, scheme_count, scheme_value, path_count, path_value with
| _, _, 1, Some ("http" | "https"), 1, Some path when String.length path = 0 ->
(* From RFC7540§8.1.2.6:
* This pseudo-header field MUST NOT be empty for http or https URIs;
* http or https URIs that do not contain a path component MUST include a
Expand All @@ -269,7 +335,7 @@ let method_path_and_scheme_or_malformed t =
* All HTTP/2 requests MUST include exactly one valid value for the
* :method, :scheme, and :path pseudo-header fields, unless it is a
* CONNECT request (Section 8.3). *)
| [ ("CONNECT" as meth) ], [], [] ->
| 1, Some ("CONNECT" as meth), 0, None, 0, None ->
(* From RFC7540§8.3:
* The HTTP header field mapping works as defined in Section 8.1.2.3
* ("Request Pseudo-Header Fields"), with a few differences.
Expand All @@ -283,10 +349,10 @@ let method_path_and_scheme_or_malformed t =
*
* A CONNECT request that does not conform to these restrictions is
* malformed (Section 8.1.2.6). *)
if mem t ":authority" then `Valid (meth, "", "") else `Malformed
| [ "CONNECT" ], _, _ -> `Malformed
| [ meth ], [ scheme ], [ path ] ->
if valid_request_headers t then `Valid (meth, path, scheme) else `Malformed
if valid && has_authority then `Valid (meth, "", "") else `Malformed
| 1, Some "CONNECT", _, _, _, _ -> `Malformed
| 1, Some meth, 1, Some scheme, 1, Some path ->
if valid then `Valid (meth, path, scheme) else `Malformed
| _ -> `Malformed

let trailers_valid t =
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